Processes for producing a sputtering target from a silicon-based alloy, a sputtering target

ABSTRACT

A process for producing a sputtering target from a silicon-based alloy with an aluminum content of 5-50 wt. %. The target material is produced by a casting technique in which the material is melted and vacuum-cast, such that the casting is carried out in a hollow cylindrical casting mold.

BACKGROUND OF THE INVENTION

[0001] The invention concerns processes for producing a sputteringtarget from a silicon-based alloy with an aluminum content of 5-50 wt.%, a sputtering target and its use.

[0002] Silicon-based alloys with an Al content of a few wt. % have longbeen known for use as sputtering targets in coating technology, forexample, see U.S. Pat. No. 5,094,288 A, and DE 198 10 246 A1. Inaddition to the planar targets that were originally used, rotatingtargets are also frequently used to produce reactively sputtered Si₃N₄or SiO₂ (EP 00 70 899). These rotating targets are usually produced byplasma spraying techniques (U.S. Pat. No. 5,853,816 A), in which eithermixtures of Si and Al elemental powders or alloy powder (DE 101 40 589)are sprayed onto a support tube. The SiAl tubular sputtering targetsobtained in this way can be produced only up to a thickness of about 6-8mm Si(Al) wall thickness, since the walls break at greater thicknessesdue to the high thermal stress to which they are subjected during plasmaspraying. Furthermore, DE 100 63 383 C1 describes a process for castingmetal tubular targets, in which the outer target coating consists of ametal with a melting point of at most 800° C., and the casting materialruns into the mold from below.

SUMMARY OF THE INVENTION

[0003] The object of the present invention is to provide a process forproducing a tubular sputtering target and a sputtering target that canbe produced as inexpensively as possible. A further object of theinvention is to specify a use for the target.

[0004] In accordance with the invention, this object is achieved by aprocess in which a sputtering target is produced from a silicon-basedalloy with an Al content of 5-50 wt. %.

[0005] The target material is produced by a casting technique in whichthe material is melted and vacuum-cast, such that the casting is carriedout in a hollow cylindrical casting mold. Preferably, the casting iscarried out in a thin-walled casting mold. It is advantageous for thetubular sections produced by casting to be soldered or cemented on asupport tube and for the tubular sections possibly to be machined beforethey are soldered or cemented on the support tube. Surprisingly, it wasfound to be advantageous for the tubular sections to be cast bytop-casting. The process makes it possible, especially as a result ofthe addition of aluminum, to produce excellent tubular sputteringtargets, which can be used in a tubular cathode.

[0006] The wall thickness of the hollow cylindrical mold is onlyslightly greater than the desired target wall thickness. The hollowcylindrical mold is filled by top-casting. Surprisingly, despite theextraordinarily broad melting range of 577° C. to a maximum of 1,380°C., one obtains a macroscopically homogeneous casting with only slightporosity and, above all, after removal of the casting mold, a crack-freetubular section.

[0007] The head of the tubular casting is separated. The casting ismachined to the necessary target dimensions on both the outside andinside diameter.

[0008] The entire tubular target is then constructed in such a way thatthe tubular sections described above are centrically positioned aroundthe support tube and integrated into a complete target by soldering orcementing on the support tube.

[0009] The invention is explained below with reference to an embodimentof the invention shown in the drawings.

BRIEF DESCRIPTION OF THE DRAWING(S)

[0010]FIG. 1 shows the casting process schematically.

[0011]FIG. 2 shows a cross section of a tubular sputtering target.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0012] A hollow cylindrical graphite mold is produced. It consists of agraphite core 1 with a diameter of 131 mm and an outer wall 2 with aninside diameter of 158 mm, an outside diameter of 170 mm, and a heightof 600 mm. An alloy of 90 wt. % silicon and 10 wt. % aluminum is melted3 in a vacuum. After complete melting of the alloy components, thetemperature of the melt is stabilized at 1,430° C. The graphite mold ispreheated to 300° C. and brought into the vacuum melting chamber, andthe molten alloy is poured into the mold cavity 7 by a mold funnel orhopper 4. After solidification of the melt and cooling of the casting tobelow 300° C., the mold can be removed from the furnace. Both the innercore of the mold and the outer wall of the mold can be removed from thecasting by a hydraulic press. The top of the cylindrical casting issawed off to a length of 100 mm. The inside diameter of the casting ishollowed out to 134 mm by turning, and the outside diameter is turned to154 mm. The inner surface of the turned casting is metallized byelectrochemical deposition with nickel strike and copper. The metallizedSi—Al tubular sections 5 are wetted with indium solder and slid onto thelikewise metallized and prewetted support tube 8. The entire target,which consists of seven SiAl tubular segments and the support tube, isheated to the soldering temperature of 180° C., and the space betweenthe outside diameter of the inner tube and the inside diameter of theSiAl castings is filled with molten indium 6. The entire tube is slowlycooled, subsequently freed of excess solder, and ground to the finaltarget dimension (d=152 mm) on an outside diameter grinding machine. Thefinished target can be installed in a commercial tubular cathode andused to produce oxidic or nitridic silicon coatings.

[0013] The invention is not limited by the embodiments described abovewhich are presented as examples only but can be modified in various wayswithin the scope of protection defined by the appended patent claims.

What is claimed is:
 1. A process for producing a sputtering target froma silicon-based alloy with an Al content of 5-50 wt. %, comprising thesteps of: melting the alloy; and vacuum-casting the alloy in a hollowcylindrical casting mold to produce tubular sections.
 2. A process inaccordance with claim 1, including casting the alloy in a thin-walledcasting mold.
 3. A process in accordance with claim 1, further includingthe step of soldering or cementing the tubular sections on a supporttube.
 4. A process in accordance with claim 3, further including thestep of machining the tubular sections, the tubular sections beingsoldered or cemented on the support tube after machining.
 5. A processin accordance with claim 1, wherein the tubular sections are cast bytop-casting.
 6. A sputtering target produced by melting a silicon-basedalloy with an Al content of 5-50 wt. %,; and vacuum-casting the alloy ina hollow cylindrical casting mold to produce tubular sections.
 7. Atubular cathode comprising a sputtering target produced by melting asilicon-based alloy with an Al content of 5-50 wt. %; and vacuum-castingthe alloy in a hollow cylindrical casting mold.